In the scene where they show Omen walking down the alley towards
, they show her from behind for a moment. This is obviously a double wearing a wig. The hair is much shorter than Omen's and is very unnatural looking.
In the scene were Danny uses the dummy head to simulate the attack, watch Danny's face shield. When he's about to hit it, before Lindsay stops him, his shield is down. When they show him again ,after Lindsay stops him, his shield is still up, so he has to put it down again.